EMG electrode apparatus and positioning system

ABSTRACT

A system for detecting and analyzing electrical activity in the anatomy of an organism underlying an electrode array provides signals corresponding to electrical activity adjacent each electrode. Such signals are correlated to the underlying anatomy of the organism and representative outputs presented through various types of output devices. Such outputs may include variations in coloration or other qualities in correspondence with representations of underlying anatomical structures. The system includes electrode structures and methods for producing and attaching electrode arrays to the organism. The exemplary form of the invention is used in connection with the diagnosis of muscle activity in the lower lumbar regions of humans. Levels of muscle activity detected are analyzed by correlation with the muscular structures underlying the electrode array. Forms of the invention may be used in other applications.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 12/106,903filed Apr. 21, 2008 (now U.S. Pat. No. 7,627,358), which is acontinuation of application Ser. No. 11/551,294 filed Oct. 20, 2006 (nowU.S. Pat. No. 7,363,069), which is a divisional of application Ser. No.11/231,025 filed Sep. 20, 2005 (now U.S. Pat. No. 7,127,279), which is adivisional of 10/641,709 filed Aug. 15, 2003 (now U.S. Pat. No.6,973,344 B2), which is a divisional of application Ser. No. 09/806,632filed on Apr. 2, 2001 (now U.S. Pat. No. 6,745,062 B1), which is anational phase application of PCT/US99/23033 filed Oct. 4, 1999 whichclaims the benefit of U.S. Provisional Application Ser. No. 60/103,105Filed Oct. 5, 1998. The above-referenced applications are herebyincorporated by referenced herein.

TECHNICAL FIELD

This invention relates to a method and apparatus for monitoring anddisplaying the condition of muscles in a muscle group by the sensing andanalysis of electromyographic signals derived from a non-invasive bodysurface electrode array positioned close to the muscle group.Particularly this invention relates to an electrode apparatus and asystem for positioning and holding electrodes in a desired orientationrelative to the anatomy of a patient.

BACKGROUND ART

Knowledge of the presence of electromyographic (EMG) signals in themuscles of humans, and the change of these signals with muscle activity,spawned development of electronic devices and techniques for monitoringthose signals for the evaluation of the muscles. Human musculature,however, involves many hundreds of muscles in various muscle groups,which interact to provide skeletal support and movement. Much of therecent development has been concerned with the techniques and/or devicesfor monitoring the signals, analyzing the information obtained andproviding reliable and useful data for the patient or treatingphysician. Recent developments in computer technology have also providedan assist in this regard. With higher speeds of operation and greatercomputing capacity, the capability for handling and operating upon amultiplicity of signals in a reasonable evaluation period has becomefeasible. However, because of the complexity of the muscle structure andthe difficulty in obtaining useful, reliable signals, preferably in anon-invasive mode, obtaining a useful definition of the muscle activityin a reasonable amount of time and in an economical manner is stillsubject to current development.

Typical of this prior art is the device described by D. Prutchi in thepublication “A High-Resolution Large Array (HRLA) EMG System”, publishedSeptember 1995 in Med. Eng. Phys., Vol. 17, 442-454. Prutchi describes abracelet which may be wrapped about a body limb and which contains 256surface electrodes to record the electrical activity of underlyingmuscles. The electrodes are arranged in eight groups of thirty-twoelectrode linear arrays directly connected to buffer boards in closeproximity of the electrodes. Further processing of the electricalsignals is performed to provide a desired signal analysis, in thisinstance primarily being concerned with the bidirectional propagation ofa compound potential in a single muscle in the upper arm of a humansubject or a histogram of total power contribution from active fibers ina subject muscle, both being presented in charted format.

U.S. Pat. No. 5,086,779 to DeLuca, et al., describes a back analysissystem of plural electrodes coupled to a computer system for processingthe signals and to provide graphical representations of results.DeLuca's invention relates primarily to isolating particular musclegroups by the use of support and restraint devices which limit themovement of the patient's torso in predetermined patterns correlated tothe desired muscle groups. DeLuca's electrode array consists of separateelectrodes individually placed at desired locations on a patient's back.

U.S. Pat. No. 5,058,602 to Brody describes a method of electromyographicscanning of paravertebral muscles comprising measuring electricalpotentials bilaterally across segments of the spine. Readings arecategorized into different patterns which are indicative of differentmuscular conditions. Brody suggests equipment useful within hisdescribed techniques as an available EMG scanner having electrodesspaced 2.5 cm apart and a computer component, but provides few detailson the equipment or an indication of usefulness for isolating certainmuscles or muscle groups.

U.S. Pat. No. 5,318,039 to Kadefors, et al., describes a method andapparatus for detecting electromyographic signals, processing them andproviding an indication of the change of the signal from a predeterminednorm. Kadefors' electrode system comprises three electrodes, one ofwhich is a reference marker. This electronic apparatus, in essence,includes a sample and hold function in which current responses can becompared to earlier responses and an indication provided based on thedifferences detected.

U.S. Pat. No. 5,505,208 to Toormin, et al., describes a method fordetermining the status of back muscles wherein EMG signals are monitoredfrom a number of electrodes placed in a pattern on a patient's back, theactivity of each electrode is determined and the results stored. Adatabase of results provides a standard from which comparisons can bemade to determine deviations or abnormalities, as a device for the careand management of the patient's dysfunction.

U.S. Pat. No. 5,513,651 to Cusimano, et al., describes a portableelectronic instrument for monitoring muscle activity, using standard ECGelectrodes and a computer for analyzing the detected signals. Theelectrodes are applied individually at predetermined locations and arange of motion device is employed to generate signals related to aparticular muscle group. Output plots are produced to provide anindication of results, apparently in the form of printouts ofinformation reflecting any deviations from the norm of expected muscleactivity.

While the prior art devices describe much sophistication in thedetection and analysis of EMG signals, there is a need for equipmentwhich is capable of being utilized by the average skilled examiningphysician who, for example, uses and is familiar with the techniques ofphysical examination and palpation of the paraspinous musculature of thethoracolumbosacral spine.

DISCLOSURE OF INVENTION

An object of the present invention is to provide improved surface EMGequipment, readily useable by the skilled examining physician, for thediagnosis or treatment monitoring of patients with low back pain.

A further object of the present invention is to provide an improvedclinical tool which is portable and which uses non-invasive techniquesfor the collection of signals.

A further object of the present invention is to provide improved EMGequipment which provides a visual display of the activity of muscles ormuscle groups.

A further object of the present invention is to provide improved EMGequipment in which the visual display of muscle activity is juxtaposedover a visual display of normal muscle anatomy for correlation by theexamining physician.

A further object of the present invention is to provide improved EMGequipment in which the visual display can be selected for specificmusculature identified by the examining physician.

A further object of the present invention is to provide improved EMGequipment which utilizes a single detector pad of electrodes in whichthe electrodes are arranged in a specific array, to monitorinstantaneously all specific muscles in a muscle group of a patient.

A further object of the present invention is to provide an improvedelectrode.

A further object of the present invention is to provide an improved EMGelectrode which achieves better signal acquisition.

A further object of the present invention is to provide an improvedelectrode that is easier to manufacture.

A further object of the present invention is to provide an electrodewith an ornamental design.

A further object of the present invention is to provide an improvedelectrode array.

A further object of the present invention is to provide an improvedsystem for holding an electrode array in contact with a patient.

A further object of the present invention is to provide an improvedmethod for positioning an electrode array relative to the anatomy of apatient.

A further object of the present invention is to provide an improved EMGdiagnostic system which provides enhanced correspondence betweencollected data and the anatomy of the particular patient.

A further object of the present invention is to provide an inexpensiveflexible electrode array.

A further object of the present invention is to provide an electricalconnector between an electrode array and a buffer/amplifier thatminimizes wear between contact points.

Further objects of the present invention will be made apparent in thefollowing Best Modes for Carrying Out the Invention and the appendedClaims.

The electromyographic (EMG) diagnostic system of the present inventionis particularly suited for evaluation of the lower back of a human andconsists essentially of a sensor pad for collecting and conditioning EMGsignals, electronic equipment including a computer for signaldiscrimination and evaluation and a display device for providing avisual display of the activity of selected musculature. A groundelectrode is positioned on the patient. The electronic equipment servesto receive signals from the sensor pad which is pressed against thelower back of a patient in a predetermined location and held immobilerelative to the patient such as by strap with foam backing, aninflatable bladder, an adhesive pad, disposable or reusable patientadhering structures or other convenient arrangement. Signals fromindividual electrodes are conditioned by the electrical equipment,discriminated from noise signals and the like and evaluated relative tothe signal received from the reference electrode. Computer apparatus isthen used to analyze the signals, and can combine the signals in variouspatterns to provide an analysis of the muscular anatomy of the lowerback and the activity of such muscles.

In an exemplary form of the invention electrodes are used which have aplurality of projections in either a pyramid or conical shape. Theconfiguration enhances acquisition of signals from the underlyingmuscles and reduces extraneous signals produced by electrolytic andother reactions with the skin of the patient and adjacent supportstructures. Such electrodes are preferably arranged in an arraysupported on a web or pad structure. The web or pad structure ispreferably flexible to conform to the contours of the patient's anatomy.The pad structure is preferably part of or connected to a releasableadhesive that adheres to the patient's skin without relative movementuntil removed. The supporting web or pad structure for the electrodesmay be reusable or disposed of after a single use.

Alternatively, an inexpensive flexible array of electrodes is formed bydepositing or printing conductive inks in the shapes of circularelectrodes on a flexible and extensible substrate sheet. A flexibleconductive adhesive such a hydrogel is deposited on the printedelectrodes to increase the sensitivity of the electrodes and to adherethe electrodes to the skin surfaces of a patient. Trace lines are alsoprinted on the substrate to route electrical signals from each electrodeto a portion of the substrate that is operative to connect with signalprocessing components such as a buffer/amplifier.

One exemplary technique for signal monitoring is to determine the RMSvoltage of the sensed signals over a predetermined time interval. TheRMS voltage is converted to a visual display representative of the powerlevel, which display then provides a visual indication of thoselocations where a higher level of muscle activity is detected. The RMSsignal technique is advantageous in providing a device for averaging thehighly sensitive and often variable individual electrode signals whichare susceptible to changes in contact resistance at the electrode, thehuman skin resistance, stray field fluctuation, inadvertent movements bythe patient, and the like, which can introduce false signals, and maskthe desired muscle activity signals.

A visual display of the sensed muscle activity is provided on a monitor,such as a cathode ray tube type monitor, which may then be evaluated bythe attending physician. A predetermined display of normal back anatomyis displayed simultaneously as an underlay on the monitor to assist thephysician in his evaluation. For example colorization of the resultantsensed display with different colors representing the degree ofcontraction thus provides a vivid indication of abnormal activity of themuscle. The display is modified to correspond to the anatomy of thepatient. Normal back anatomy is provided in this invention by theselection from an inventory of various back muscle configurations whichdepict different layers of back muscles of the normal human patient.These configurations are selectable by the physician for comparison withthe sensed muscle activity pattern in order to assist in providing acorrelation between the two. Further control is provided in that thephysician not only can alter the physical configuration of the sensedsignal display but also can adjust the intensity or colorization of thesensed display to render a more pronounced image of abnormal muscleactivity relative to normal back anatomy. Visual display modification isachieved by adjustment of the sensitivity of the sensed signal detectoror by increasing the level of signal over which a visual indication isprovided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a simplified schematic overview of a portion of the lower backskeletal structure of a patient with an outline of the sensor padportion of the invention depicted in position thereover.

FIG. 2 is a schematic view of the apparatus of the invention, comprisingthe sensor pad in connection with electronic apparatus including acomputer and display unit.

FIG. 3 is a schematic view of the screen of the display unit of theinvention showing a full color bar matrix overlay in relation to thelower back skeletal anatomy of a human patient.

FIG. 4 is a view partly in cross-section of a portion of the sensor padof the invention, showing a single electrode and the electricalconnection to the computer portion of the invention.

FIG. 5 is an enlarged plan view only of the single electrode shown inFIG. 4.

FIG. 6 is a cross-sectional view of a single electrode taken along thelines 6-6 of FIG. 5.

FIG. 7 is a schematic view of the screen of the display unit of theinvention depicting the location of a portion of the electrodes of thesensor pad as circles and showing several interconnecting color bars.

FIG. 8 is a schematic view of the lower torso of a patient with thesensor pad held in position by a retaining belt and a support pad.

FIG. 9 is a plan view with parts removed of the retaining belt of FIG.8, showing the support pad.

FIGS. 10-13 are schematic views of the screen of the display unitshowing various configurations of color bar displays.

FIG. 14 is a schematic diagram of skeletal anatomy associated with thelower back of a normal human patient.

FIGS. 15-23 are schematic diagrams of various groups of musculature of anormal human patient shown in relation to the skeletal anatomy of FIG.14.

FIG. 24 is a schematic view of the apparatus of the invention, similarto that of FIGS. 2 and 4, in a modified showing of the interrelation ofcomponents of the invention.

FIG. 25 is a schematic view of the components comprising the AnalogSignal Conditioning Subsystem of FIG. 24.

FIG. 26 is a schematic view of the components comprising the SignalProcessing Subsystem of FIG. 24.

FIG. 27 is a logic diagram showing the data flow in the software of thesystem.

FIG. 28 is a chart of a portion of the software program of theinvention, showing a header format.

FIG. 29 is a chart of a portion of the software program of theinvention, showing a listing of files developed therein.

FIG. 30 is a chart of a portion of the software program of theinvention, showing generally the Source File Structure.

FIG. 31 is a front isometric view of an alternative electrodeconfiguration.

FIG. 32 is a back isometric view of the alternative electrode shown inFIG. 31.

FIG. 33 is a back plan view of the alternative electrode shown in FIG.31.

FIG. 34 is a cross sectional view of the alternative electrode takenalong line 34-34 in FIG. 33.

FIG. 35 is a side view of the alternative electrode.

FIG. 36 is a front plan view of the alternative electrode.

FIG. 37 is a rear plan view of an electrode array and self adhesiveelectrode support pad.

FIG. 38 is a front plan view of the self adhesive support pad shown inFIG. 37 without electrodes mounted thereon.

FIG. 39 is an isometric view of a reusable electrode support pad andremovable adhesive web for use in connection with the reusable electrodesupport pad.

FIGS. 40, 41 and 42 are back, top and front views respectively, of theelectrical component holster supporting belt worn by a patient inconnection with self adhesive electrode array supporting pads.

FIG. 43 schematically represents an exemplary embodiment of a flexibleelectrode array.

FIG. 44 is representative of a cross sectional side view of thedeposited materials comprising the flexible electrode array

FIG. 45 is representative of a cross sectional bottom view of thedeposited materials comprising the flexible electrode array.

FIG. 46 schematically represents a portion of the flexible electrodearray with a plurality of printed electrodes and trace lines withstrategically cut perforations in the substrate for enhancingflexibility and extensibility of the electrode array.

FIG. 47 is representative of a top plan view of the electrode array withthe printed electrode flexing away from its original position cut in thesubstrate.

FIG. 48 is representative of a cross sectional side view of a electrodearray connector.

FIG. 49 is representative of a cross sectional front view of theelectrode array connector.

FIG. 50 is representative of a top plan view of the electrode arrayconnector.

FIG. 51 is representative of a bottom plan view of a head member of theelectrode array connector.

FIG. 52 is representative of an isometric view of a buffer/amplifiercoupled to the electrode array connector.

FIG. 53 is representative of an isometric view of a housing enclosingthe buffer/amplifier coupled to the electrode array connector.

BEST MODES FOR CARRYING OUT INVENTION

Referring now to the drawings, and initially to FIG. 1, there is shownin schematic form the sensor pad 10 of the invention positioned inrelation to a partial skeletal showing of the lower back of a patient,the latter comprising a spine 11, left posterior superior iliac crest12, right posterior superior iliac crest 14, portions of the scapula 15and ribs 16. As will be described in greater detail hereafter, sensorpad 10 is a device for collecting electromyographic (EMG) signals fromthe underlying muscle structure supporting and providing movement to thespine 11. The muscle structure is a complicated array of musclesconsisting of at least sixty-nine erector and intrinsic muscles in thethoracolumbosacral spine extending from about the tenth thoracicvertebrae 18 to the sacrum 20. These are the primary muscles with whichthis invention is concerned and occur in layers from deep tosuperficial. Also formed in the superficial region of the lower back areseveral muscles which are not classical erector muscles, which whileimportant, are not the principal interest of this invention. Theselatter muscles may also produce EMG signals which serve to complicatethe evaluation process and may require discrimination, but which are nota primary source of the lower back pain syndrome affecting the greaterportion of the patient population.

EMG signals and their relation to muscle functions are well understoodat the current state of investigations. Muscles are controlled bynerves, the latter transmitting an electrical signal to a particularmuscle and causing contraction thereof. The muscle itself is a volumeconductor reacting to the signal of the associated nerve. There is avoltage change that occurs when a muscle contracts creating an electricpotential that is directly proportional to the strength of contractionand that can be captured from the external surface area of the patient,in this instance being the surface area of the thoracolumbosacral spine.Currently, there is technology which allows certain evaluations of theelectrical activity of muscles such as EMGs or EKGs and which may bedisplayed in analog, waveform or spectral forms. Available technologyand the associated devices however are deficient in not being able toselect all muscles in a muscle region in a manner which is conducive toevaluation by an attending physician.

Referring now to FIG. 2 there is shown in schematic form, the essentialelements of this invention as comprising sensor pad 10 and electronicapparatus 22 comprising preamplifier 23, converter 24, computer 25 anddisplay unit 26. Sensor pad 10 in a first embodiment is a flatrectangular piece of siliconized rubber, approximately 0.157 cm (0.062inch) thick, measuring about 30.48×30.48 cm (12×12 inches) and with aDurometer hardness on the order of 20 to 40. One source for sensor pad10 is Fairprene Industrial Products, Inc. of Fairfield, Conn.

Sensor pad 10 further comprises an array of sixty-three electrodes 28,which may be made of 316 L stainless steel, silver or other materials.Electrodes 28 are preferably arranged in a 7×9 pattern, with theelectrodes in each row and column being spaced 2.95 cm (1.162 inches)apart on center. A central column 29 of nine electrodes 28 is located inthe middle of sensor pad 10 to overlay the spine 11 of the patient, andthree equally spaced parallel columns of nine electrodes each arepositioned on either side of the central column 29. Similarly, a centralrow 30 of seven electrodes 28 is positioned near the center of sensorpad 10, and four parallel rows of seven electrodes each are positionedon either side of central row 30. Ground electrode 31, is a standardelectrode preferably positioned on a wrist of the patient. Of course inother embodiments other configurations may be used.

All of the electrodes 28, are preferably identical and one configurationis shown in greater detail in FIGS. 4-6 as comprising a pyramidaltipped, bolt-shaped structure having a head 32 and integral threadedshaft 34. Head 32 is circular and includes a plurality of pyramids 35distributed substantially evenly and projecting outwardly of the uppersurface of head 32 to form the patient-contacting surface of electrode28. Head 32 is preferably about 0.95 cm (0.375 inches) in diameter andhas a thickness of about 0.20 cm (0.08 inches) from the lower surfacethereof at the junction with shaft 34, to the tips 36 of pyramids 35.Pyramids 35 are formed by grinding electrode head 32 in a series ofparallel and orthogonal passes or by electromachining to produce asquare pyramidal shape having an altitude of about 0.107 cm (0.042inches), an angle of about 90 degrees between opposing pyramid faces andculminating in a tip 36 having a radius of about 0.0127 cm (0.005 inch).Tips 36 are spaced about 0.2387 cm (0.094 inches) from one another andin this embodiment of the invention, result in an electrode 28 havingtwelve pyramids 35 and tips 36 at the signal-collecting surface thereof.It has been determined that this configuration of electrode 28 is usefulin enhancing lower contact resistance when placed in position on apatient, thereby assuring better EMG signal reception and greateraccuracy of the measurement.

Each electrode 28 is mounted in an aperture in sensor pad 10 andretained in position by a nut 170 threaded to shaft 34. Alternatively,electrode 28 may have an unthreaded shaft 34 and be retained in positionby a push connector. A solderless ring connector 38 is also received onshaft 34 and is firmly secured by outer nut 39 to provide an electricalinterconnection with the signal gathering surface of electrode 28. Anelectrode wire 40 is crimped to connector 38 and each of the electrodewires 40 is routed over the surface of sensor pad 10 to a pigtail at theupper end of sensor pad 10 which terminates at a connector 41. Eachelectrode wire 40 is preferably a 30 gauge, multi strand, flexiblecopper wire which allows for some deformation of sensor pad 10 toconform to the lower back of a patient, while connector 41 allows forreleasable connection of the sensor pad to the electrical circuitry tofacilitate substitution of components of the apparatus of the invention.With an electrode head 32 diameter and spacing, as mentioned in thedescribed embodiment, the edge to edge spacing of electrodes 28 in eachcolumn 29 and row 30 is about 2.0 cm (0.79 inches). This has beendetermined to provide enough distance between electrodes 28 to result ina meaningful signal difference between electrodes. Electrode 28 may alsobe used in connection with the reusable or disposable self adhesivesensor pads which are later discussed in detail.

An alternative electrode 200 used in connection with embodiments of theEMG diagnostic system of the invention are shown in FIGS. 31-36.Electrode 200 includes a head portion 202 and a stem portion 204. Thestem portion is suitable for electrical connection with electrode wiresin a manner similar to the previously described embodiment.

The head portion of the electrode 200 includes a base surface 206 and aplurality of conical projections 208 extending forward therefrom. Theconical projections 208 in one exemplary embodiment are comprised ofnested circular arrangements of six cones each. A first set 210 of sixcones is spaced in close relation about a central projection 212. Asecond set 214 of six cones is spaced in outward nested relationrelative to the first set 210. A third set 216 is disposed outwardlyrelative to the second set 214. Each of the cones in the third set 216are spaced in nested relation between cones in the second set. In theexemplary form of the invention each of the cones are arrangedconcentrically about the central projection 212 as shown in FIG. 36.

In one embodiment of the alternative electrode 200 the base surface isapproximately 1.066 cm (0.420 inches) in diameter and the stem portionis approximately 0.318 cm (0.125 inches) in diameter. In this embodimentthe first set of conical projections is spaced in a circle of about0.391 cm (0.154 inches) in diameter. The second set of six cones isspaced on a circle about 0.678 cm (0.267 inches) in diameter and thethird set of cones is spaced on a circle about 0.782 cm (0.308 inches)in diameter. Of course in other embodiments other configurations may beused.

The exemplary configuration of the conical projections provides for theprojections to extend about 0.071 cm (0.028 inches) above the basesurface. The incident angles of the walls bounding the cone extend at anangle C as shown in FIG. 34 which is about 79 degrees. The tips of thecones are rounded and have radii of about 0.0127 cm (0.005 inches). Thethickness of the electrode 200 underlying the base surface is generallyabout 0.053 cm (0.021 inches). Of course in other embodiments otherconfigurations may be used.

In the exemplary form of alternative electrode 200 the electrode iscomprised of an ABS carbon-composite resin material. The ABS resin ispreferably provided with a coating of a suitable conductive materialwhich in the exemplary form of the electrode is a silver/silver chloridematerial. The coating is preferably deposited on the ABS resin body byelectroplating, vacuum metallization or similar processes. Inalternative embodiments other approaches may be used.

A useful aspect of the described embodiment of the alternative electrode200 is that the plated electrode contacts the patient's skin with amaterial that has a minimal electrolytic reaction with the skin of thepatient. This minimizes the electrolytic currents which are produced asa result of contact and produces improved signals. In addition thearrangement of nested conical surfaces provides a relatively largersurface area for contact with the skin. The conical projections extendinward relative to the normal contour of the skin to provide signalacquisition from this area. This further enhances the ability of theelectrode to acquire signals produced by the underlying anatomy. Thestructure of the exemplary form of the alternative electrode is alsoeconomical and may be produced using cost effective manufacturingprocesses. Further the exemplary form of the electrode provides anattractive and ornamental design.

The electronic circuitry comprising preamplifier 23 is located nearsensor pad 10 for conditioning and amplifying the signals received atelectrodes 28. Electrode wire 40 is connected to buffer amplifier 42,and the signal in turn is routed to low pass filter 43 and high passfilter 44 for each electrode 28 of sensor pad 10. Conditioning of thesignals preferably occurs closely adjacent the patient and avoids remotetransmission of very low level signals in a background of randomlygenerated noise signals. Buffer amplifier 42 minimizes leakage currentthrough the electrode and errors due to electrode impedance changes.High pass filter 44 serves as an anti-aliasing filter, and low passfilter 43 prevents saturation of analog to digital (A/D) converter 24 byoffset voltages, such filters being well understood in the art.

As shown in FIG. 24 preamplifier 23 includes Buffer/Amplifier module 42and Filter/Buffer module 105. Cable 45 connects the components ofpreamplifier 23 to analog to digital (A/D) converter 24 for transmissionof the electrode signals for further processing and analysis.

Sensor pad 10 is applied to the back of a patient by orienting certainof the electrodes 28 to the skeletal structure of the patient. In oneembodiment central electrode in the top row of electrode rows 30, i.e.,electrode 46 is located over the spinous process of the tenth thoracicvertebrae 18. Two other landmarks are identified in a similar manner asthe sensor pad 10 overlays the mid portion of the posterior superioriliac crest (PSIS). For example, the second and sixth electrodes 33, 37respectively, in the center row of electrode rows 30 may be over theleft PSIS and right PSIS. Alternatively, other landmarks may be used,such as an electrode overlying the fourth lumbar vertebrae, or otherphysiological reference point. This calibration information is then fedinto the electronic apparatus 22 for appropriate adjustment of thevoltage data received from electrodes 28 and subsequent visual displayrelative to predetermined displays of muscular anatomy appearing atdisplay unit 26, in order to assure standardization of electrodeplacement.

In alternative forms of the invention an alternative protocol may beused for positioning and locating the electrode array. Such methods maybe used in connection with sensor pad 10 as well as the reusable andself adhesive sensor pads later discussed.

Locating of the sensor pad begins with the patient in a neutral uprightposition. The patient's feet are preferably shoulder width apart, thehead and face forward. The clinician positioning the electrode array maypalpate both the left and right superior iliac crests to locate theirposition. Drawing an imaginary line directly between these two points,the clinician palpates the spinous process at this level which is L4 thefourth lumbar vertebrae. The clinician then marks the L4 spinous processwith a water soluble marker. The electrode positioned in the middlecolumn and seven rows from the top is then positioned directly over theL4 indicator. This electrode is marked 47 in FIG. 2.

Continuing with the location and calibration process, once the L4electrode has been positioned the clinician palpates the most inferiorpoint of the inferior angles of both scapulae. The clinician thenenvisions an imaginary line between these two points and palpates thespinous process at this level. This is the seventh thoracic vertebraeT7. The clinician may then use calipers or other suitable measuringdevice for measuring from the T7 spinous process to electrode 47 at L4.This measurement may be recorded, or in some embodiments input to thecomputer through an input device for correlating the output to thedimensions of the patient's anatomy in a manner that is later discussed.

Continuing with the protocol, with the patient in the same position theclinician finds the left superior iliac crest at its most lateral point.Using calipers or other measuring device the clinician measures from themost lateral aspect of the left iliac crest to the electrode at L4. Thismeasurement is also recorded or in some embodiments input to thecomputer through an input device.

In some embodiments of the invention the computer 25 includes softwarewhich is operative to scale outputs displayed responsive to theconfiguration of the patient's anatomy. This is achieved because thedimensions of the patient are known as are the distances between theelectrodes. In this manner the computer is enabled to calculate orotherwise determine how the anatomical features underlying theelectrodes correspond to the electrode positions for the givendimensional configuration of the patient. This enables signals fromelectrodes to be more accurately correlated to underlying anatomicalstructures, such as muscles which are exhibiting spasmodic conditions.

Referring now as well to FIGS. 8 and 9, there is shown in two views themechanism for attachment of sensor pad 10 to the lower back of a humanpatient 48. A type of lumbar support belt 49 encircles part of the lowertorso of patient 48 and is retained in place by several straps 50 ofnon-elastic web culminating in quick release snaps 51 at the endsthereof for adjustment and securement. Belt 49 includes a pouch thereinin which is disposed a molded foam pad 52. Pad 52 is generallyrectangular in configuration and about 2.54 cm (one inch) in thicknessat its midpoint and tapering to about 0.3175 cm (0.125 inch) thicknessat its left and right edges. The pad has a curved inner surfacegenerally conforming to the curvature of the lower torso of a typicalpatient 48 and overlying sensor pad 10 to press the latter into securephysical contact with patient 48 as straps 50 are adjusted. Preferably,belt 49 is about five cm (two inches) larger than the operative portionof sensor pad 10, and pad 52 is also slightly larger than sensor pad 10,thereby to overlap the latter and assure fairly uniform pressure overthe entire area of sensor pad 10 and consistent readings from electrodes28.

Preferably, pad 52 has three parts, namely parallel vertical sections 53and a central stiffer section 54. Pad 52 is firm, yet flexible, andthicker in the central section 54 than in the outer sections 53 asdescribed above. In this manner a better fit is made to accommodate thecontour of the human back. Support belt 49 is preferably made ofnon-elastic nylon material as are straps 50 to achieve a secure andreliable connection to the patient 48.

Preferably, a conductive gel is applied to electrodes 28 (or alternativeelectrodes 200) to enhance conductivity of the interface betweenelectrodes and patient 48, as is well known in the art. One suitablebrand of water soluble gel is that manufactured by TECA, a subsidiary ofVickers Medical, Inc. Alternative approaches to locating and securingthe electrodes to a patient may be used. For example FIG. 37 discloses adisposable sensor supporting pad or sheet generally indicated 220.Sensor supporting sheet 220 comprises a flexible web material that isrelatively thin and sufficiently flexible to conform to the contours ofthe patient. As shown in FIG. 38 web material 222 includes apertures 224therethrough. Apertures 224 are sized for accepting the head portions ofelectrodes designated 226 therethrough. The electrodes may be of thetype described herein or other types. For example when electrodes 200are used the apertures 224 are sized such that the head portion of theelectrode is enabled to contact the skin of the patient in the area ofthe conical portions 208. The front face 228 of the web material 222preferably includes an adhesive thereon. The adhesive is preferably madeto adhere to the skin of the patient once adjacent thereto, but may bereleased from the skin in response to a less than harmful removal force.The adhesive material applied on the front face is preferablysufficiently strong once adhered to prevent relative movement of theelectrodes on the skin of the patient until the web material is removedby a clinician. The adhesive material on the front face 228 ispreferably covered by a separable cover sheet which covers the adhesivematerial until the sensor supporting sheet is ready to be applied to apatient.

As shown in FIG. 37 the electrodes 226 are held to a rear face 230 ofthe web material 222. This is accomplished in the embodiment shown bysupport discs 232. Support discs 232 are preferably flexible sheetmaterial with an adhesive or similar flexible attaching means thereonwhich adhere to both the electrodes and the rear face 230. The supportdiscs include an opening therethrough which enables wires or otherelectrically conducting elements 234 to extend therethrough to contactthe electrodes. It should be understood that while electrical wires areshown in the embodiment described in connection with FIG. 37, in otherembodiments other types of electrical conductors such as electricaltrace conductors or other types of conducting means may be used. Asshown in FIG. 37 the wires 234 terminate at electrical connectors 236and 238. The electrical connectors are adapted to connect the wires andthe associated electrodes to the remainder of the system.

The disposable electrode array which includes sensor supporting sheet220 is useful because it is sufficiently flexible to conform to thecontours of a patient's anatomy. Further the adhesive material securesthe electrode in contact with the patient's skin and generally preventsrelative movement until the sensor array is ready to be removed. Thedisposable character of the sensor supporting sheet also reduces timeassociated with cleaning components between patients. The components ofthe system are preferably assembled in a manner that enables the wiresand electrodes to be readily disconnected, cleaned and recycled into newsensor supporting sheets.

An alternative configuration for supporting an electrode array is shownin FIG. 39. In the embodiment shown in FIG. 39 the electrodes aresupported on a flexible resilient pad 240. Pad 240 is preferablycomprised of silicone or other material sufficiently flexible to conformto the contours of a patient's body. Electrodes designated 242 arepositioned in supporting connection with the pad. Electrodes 242 may bemounted in apertures that extend through the pad 240 in someembodiments. Alternatively electrodes 242 may be in molded connectionwith the pad. In addition the wires which extend to the electrodes 242may also be molded into the pad to facilitate connection to theelectrodes and to minimize the risk of damage.

A double stick adhesive web or sheet 244 is positioned adjacent to pad240. Adhesive sheet 244 includes apertures 246 that extend therethrough.The positions of apertures correspond to the positions of electrodes 242such that the heads of the electrodes may extend therethrough. Adhesivesheet 244 includes adhesive on the side adjacent to the pad 240 whichserves to adhere to the adhesive sheet thereto. However the nature ofthe adhesive and the sheet material is such that the adhesive sheet onceadhered to the underlying pad may be removed therefrom without damagingthe pad or the electrodes.

The adhesive sheet 244 further includes an adhesive material on the sideopposite the pad 240. This adhesive material is suitable for adheringthe sheet 244 and the attached pad 240 to the skin of the patient in amanner similar to the sensor supporting sheet 220. The adhesive sheet244 preferably includes a reversible cover sheet or similar itemattached to the patient side thereof to maintain the adhesive generallydirt free until the sheet is ready to be adhered to the back of thepatient. When the pad 240 is ready to be brought into contact with thepatient's back the sheet covering the adhesive on the patient's side ofsheet 244 may be removed. The pad 240 may then be positioned andconformed to the contours of the patient and the signals from theelectrodes may then be analyzed as later discussed. When the analysisand other activities are complete the pad 240 and sheet 244 may beremoved from the patient's back.

A useful aspect of the structure shown in FIG. 39 is that the adhesivesheet will generally absorb the dirt, hair and other material collectedfrom the patient. After use the sheet 244 may be separated from theadhesive pad 240. The surfaces of the electrodes may then be cleaned andthe pad made ready for reuse. The ability to collect hair and othermaterial on the disposable adhesive sheet 244 reduces the time requiredfor cleaning the electrodes and pads. Of course in other embodiments ofthe invention other approaches may be used.

When the electrode arrays shown in FIGS. 37 and 39 are used there isgenerally no location on the structure supporting the electrode array tomount the electronics components for amplifying and conditioning thesignals which are derived from the electrodes. As previously discussed,it is advisable to condition and/or amplify such signals as close to thesource as reasonably possible to avoid the introduction of extraneoussignals. To achieve this goal the holster and belt combinationdesignated 248 and shown in FIG. 40-42 is used. Holster belt 248includes an adjustable belt portion 250 which can be sized to besupported around a suitable area of the patient. In most cases this willbe the patient's waist or hips. A quick release buckle or a reversiblesnap including a first end 252 and a cooperating second end 254 areattached to the belt portion.

A first pocket 258 and a second pocket 260 are supported on the beltportion 250. Each of the pockets preferably includes electricalconnectors which provide an electrical connection with connectors fromthe electrode array such as connectors 236 and 238 shown in FIG. 37.Pockets 258 and 260 also preferably include electrical signalconditioning components which are desirable to place adjacent to thepatient. This may include for example the preamplifiers and other signalgenerating or conditioning circuitry for conditioning the electrodesignals. Pockets 258 and 260 may also include further connectors foroutputting the conditional electrical signals therefrom.

It should be understood that the described form of the holster belt 248is exemplary and in other embodiments other approaches to supporting theelectrical connectors and signal conditioning components may be used.These may include for example supporting such components on otherstructures supported by the patient or on other types of supportstructures which are not supported by the patient.

FIG. 43 schematically represents an alternative exemplary embodiment ofthe electrode array 280. Here both the electrodes 284 and electricaltraces 286 are formed by depositing or printing electrically conductiveinks on a flexible non electrically conductive substrate 282. In thisdescribed exemplary embodiment the substrate 282 is a sheet of polyestersuch as Mylar®; however, in other embodiments other flexible materialsthat are operative to support conductive materials may be used.

A plurality of the electrodes 284 are printed on the substrate 282 in apredetermined pattern. In this described exemplary embodiment theelectrodes 284 are printed in uniform array 314 of nine by sevenelectrodes. Each electrode is printed in the shape of a solid circlewith a diameter of about 1.27 cm (0.5 inches). However, in otherembodiments other sizes, shapes, and patterns of electrodes can beprinted based on the desired sensitivity and intended use for theflexible electrode array. Other examples of possible electrode shapesinclude hexagons and stars.

At lease one trace is printed on the substrate 282 for every electrode.The traces are printed in a pattern such that the traces are inelectrical connection with the electrodes. The traces then converge intotwo groupings 288 and 290 of parallel trace lines. In this describedexemplary embodiment the substrate is cut to include two long tails 292and 294. The groupings of parallel traces 288 and 290 are printed alongthe tails 292 and 294 and terminate at connection ends 296 and 298. Theconnection ends are printed in a pattern that is operative to mate withan external electrical connector such as the Zero Insertion Force (ZIF)connector discussed later in detail. For this described exemplaryembodiment the center electrode 316 is used as a reference electrode andmay be connected to one or more additional trace lines.

When in use with the computerized EMG diagnostic system, the mid section300 of the flexible electrode array is placed against the back of apatient. The tails 292 and 294 have sufficient length and flexibility towrap around the torso of the patient and to connect to additionalconditioning circuitry such as buffer/amplifiers. The additionalcircuitry may be located in the pouch of a holster belt as discussedpreviously or may be connected to a belt with a clip or other attachmentdevice such as snaps or velcro.

FIG. 44 is representative of a cross sectional view of the flexibleelectrode array 302. In this described exemplary embodiment eachelectrode 304 is silk screen printed on the substrate 306 with a highlyconductive printing material such as a silver/silver chloride epoxy ink.A conductive self supporting adhesive 308 such as hydrogel is stenciledover each printed electrode and UV cured in place. In alternativeembodiments the hydrogel can be cured by other means including thermalcuring. The hydrogel provides additional electrical conductivity betweenthe surface of a patient's back and the printed electrode. In additionthe hydrogel enables each printed electrode to adhere to a patient'sback with sufficient adhesive strength to support the flexible electrodearray in place.

In this described exemplary embodiment, traces 310 are silk screenprinted on the substrate 306 with a silver epoxy ink 310. As shown inthe cross-sectional bottom view of FIG. 45, each trace 310 includes acircular end 311. The silver/silver chloride epoxy ink of the electrode304 is printed over the silver epoxy circular end 311 of the trace 310to provide a strong electrical connection between the electrode and thetrace deposits.

In addition, the more narrower trace line portions 309 of the traces 310are insulated by printing additional layers of a non conductive ink 312over the trace lines 309. In this described exemplary embodiment eachconductive trace line is about 0.05 cm (0.02 inches) in width. Theinsulating ink line is centered over each conductive trace line and hasa width of about 0.2 cm (0.08 inches). In alternative embodiments tracelines 309 may have variable widths so that the impedance of each traceis the same, even though the trace lines have different lengths.

Although in this described embodiment the electrodes and traces are silkscreened on a substrate, in alternative embodiments, the flexibleelectrode array can be produced by any process that is operative todeposit or print a specifically defined pattern of conductive materialson a flexible sheet. Examples of such other processes includesflexographic printing with conductive inks. In other embodimentssubtractive methods can be used such as chemical etching of aluminum orcopper on clear polyester.

In addition, rather than insulating trace lines with non conductiveinks, other embodiments may include a non conductive overlay sheet forinsulating the printed trace lines. Such an overlay would leave theelectrodes and connector ends exposed by including a plurality ofapertures in the overlay which coincide with the printed electrodes andconnector ends.

One advantage of printing both the electrode and the traces on a clearflexible plastic substrate such as polyester sheet is the reduction inthe cost associated with manufacturing the flexible electrode array. Thelower cost enables the flexible electrode array to become a disposablepart in the computerized EMG diagnostic system; thus, eliminating theneed to clean electrodes between uses of the system. In addition, usinga transparent substrate such as a polyester sheet, aids in the accuratepositioning of the electrodes by allowing a clinician to see theunderlying anatomy of the patient through the flexible electrode array.Thus, after a clinician has marked the locations of vertebra on apatients back, the clinician can precisely position the center column ofthe printed electrodes over these markings.

Another advantage of using a polyester substrate such as Mylar®, is thatpolyester film is a material that is both tear resistant andsufficiently flexible to conform to the general shape of a patient'sback. Further, the present invention achieves increased flexibility andextensibility in the design of the flexible electrode array by includinga plurality of strategic slits in the substrate to make the flexibleelectrode array extensible (stretchy) in between electrodes. Thisenables the flexible electrode array to stretch or compress in threedirections (horizontal, vertical, and diagonal).

FIG. 46 is representative of a portion of a flexible electrode array320. In this exemplary embodiment of the array, the substrate 318 isstrategically cut to include a plurality of cuts or perforations 324through the substrate that are located along the outside perimeter ofeach printed electrode 322. In the exemplary embodiment the perforationsextend through the substrate. However, in alternative embodiments, theperforations need not go all the way through the substrate.

These perforations 324 also extend along each trace 326 adjacent anelectrode 322 to form a stem portion 323 of the substrate that supportseach trace. These perforations enable each printed electrode 322 and theelectrode supporting portion of the substrate 325 to move in a pluralityof directions with respect to the rest of the substrate 340, whileremaining in electrical communication with the remainder of theelectrode array. For example FIG. 47 shows a top perspective view of theprinted electrode 322 and the electrode supporting portion of thesubstrate 325 that has been bent or flexed away from the perforation 324in the supporting substrate 330.

When the entire flexible electrode array is placed on a patient's back,each electrode adheres to the skin of the patient's back. As the patientmoves into different positions, the printed electrodes are operative tomove with respect to each other in response to the patient's backmuscles stretching or contracting.

Referring back to FIG. 46, this described exemplary embodiment alsoincludes additional parallel perforations 332 in the substrate. Theseslits are grouped into a plurality of sets 334 and 336 which extendalong the entire length of the substrate. These parallel perforationsenable the substrate to stretch in one or more directions with themovement of a patient's back. Along with the perforations 324 around theindividual electrodes, these parallel perforations 332 further enablethe flexible electrode array to stretch or flex responsive to movementof back muscles, without individual electrodes being pulled away fromtheir original positions on the patient's back.

As shown in FIG. 43, this described exemplary embodiment of the flexibleelectrode is protected by a removable cover sheet 301 that is placed ontop of the array of printed electrodes 314. The hydrogel is sufficientlysticky to support the removable cover sheet 301 in place prior to theflexible electrode array being used. To separate the removable coversheet 301 from the underlying array of electrodes 314, the cover sheetis typically peeled away from the flexible electrode array starting atthe top 338 of the flexible electrode array.

As shown in FIG. 46 the perforations are located around the electrode322 and trace 326 such that the stem portions 323 of the substrate areoriented in a common direction. One advantage of this particularpattern, is that when the removable cover sheet 301 is pealed awaystarting at the bottom 338 of the flexible electrode array 320, theprinted electrodes will not be pulled away from the base substrate 340at an odd angle which may tear the electrode supporting portion 325and/or stem portion 323 from the remaining portions of the substrate340.

This described embodiment of the flexible electrode array alsoencompasses a release sheet adhesively attached to the substrate on theside opposite the previously described cover sheet 301. As shown in FIG.46, the release sheet 350 includes a plurality of rectangular apertures351 which result in the release sheet having of a grid pattern with aplurality of rows 352 and columns 354. The rows and columns arepositioned along the release sheet 350 to intersect with the electrodesupporting portions 325 of the substrate. The release sheet is attachedto the substrate 340 with a removable/repositionable adhesive.

For this described exemplary embodiment the flexible electrode 348 arrayis sandwiched between the cover sheet and the release sheet 350. Thisconfiguration helps protect the flexible electrode array duringshipment. When a clinician applies the flexible electrode array to apatient, the cover is first removed; however, the release sheet is lefton the flexible electrode array. As the clinician aligns the flexibleelectrode array 348 on the patient's back, the release sheet 350prevents the electrode supporting portions 325 from moving relative tothe substrate 340. Once the flexible electrode array is positionedcorrectly on the patient, the release sheet is removed.

In addition to applications for diagnosing back muscle problems, Thisdescribed exemplary embodiment of the flexible electrode array can alsobe used in other types of diagnostic applications such as around bodyjoints, the neck, a hand or foot, or any other area of the body that isoperative to bend or flex or is curved. In such cases the pattern andsizes of electrodes can be printed on the flexible supporting sheet tosuit the particular application. For instance, when diagnosing problemswith a hand such a carpel tunnel, the supporting sheet could be cut inthe shape of a hand. Individual electrodes may then be printed alongportions of the supporting sheet to correspond with fingers, the back ofthe hand, and the wrist. For other body parts, other shapes and patternsof electrodes can be used.

The exemplary embodiment of the flexible array as shown in FIG. 43,includes a pair of connection ends 296 and 298. Each of the electricaltrace lines terminates at one of these connection ends. To aid in thecoupling of the trace lines to an external electrical connector, thetrace line ends in connection points 299 which have an exposedelectrically conductive surface and have a size that is operative tomate with electrical contacts of an electrical connector.

To help protect the exposed connection points 299 from damage duringshipment and storage and from accidental contact with a ground orvoltage source, the connection ends 296 and 298 include tail flaps 360and 362. As shown with reference to tail flap 362, only an end portion366 of the tail flap 362 is attached to the connection end 298. The tailflap 362 is comprised of a flexible material that enables the portionsof the tail flap 362 above the connection points to be lifted away fromconnection points 299. In this described embodiment the tail flap 362includes tabs 370, and 372 which assist in lifting the tail flap by handor by an electrical connector when the connection end is inserted intoan electrical connector.

An exemplary embodiment of an electrical connector 400 is schematicallyshown in FIGS. 48-50. This exemplary connector 400 was specificallydesigned to mate with the connection ends of the flexible electrodearray. The connector 400 is a ZIF connector so that wear is minimizedbetween the connector 400 and the connection ends of the flexible array.This extends the usable life of both the connector and the flexiblearray, thus enabling many mate-demate cycles.

FIG. 48 shows a side plane view of the connector 400 which includes abase member 402. The base member includes a first surface 404 thataccepts the connection end 406 of the flexible array adjacent to thefirst surface 404. The connector 400 also includes a head member 408that is operative to move with respect to the base member 402. The headmember 408 includes a second surface 410 that faces the first surface404 of the base member 402.

The head member 408 is operative to move between a closed position andan open position. In the closed position the head member 408 isoperative to clamp the connection end 406 between the first and secondsurfaces 404 and 410. When the head member 408 is in the open position,a throat area 407 is formed between the first and second surfaces 404and 410 with sufficient space to enable the connection end 406 to freelymove in and out of the throat area 407.

The connector further includes head guide 419 with a head bore 421therethrough. The head member 408 includes a follower member 420 thatextends in a direction opposite of the second surface 410 and throughthe bore 421. The follower member 420 is operative to slide back andforth within the head bore.

In the exemplary embodiment, the head member is biased toward the closedposition with a spring 422 located between the head guide 419 and thehead member 408. However, in alternative embodiments the head member maybe biased in the open position.

As shown in FIG. 49, the connector further includes a shaft guide 413with a shaft bore 415 therethrough. The shaft bore is sized to accept ashaft member 412 therethrough. The shaft member 412 is operative torotate within the shaft bore 415. The shaft member includes a camsurface 414 that is in slidable contact with a cam follower surface 423of the follower member 420. As the shaft member turns, the cam surface414 is operative to urge the follower member 420 to move within the headbore 419, which in turn moves the head member 408 away from or towardthe base member 402.

As shown in FIG. 50, the connection end 406 of the flexible arrayincludes a plurality of traces 416. As shown in FIGS. 48 and 49, thesecond surface 410 of the head member 408 includes a printed circuitboard 411 with a plurality of electrical contacts 409. As shown in FIG.51, these electrical contacts 409 are arranged in a predeterminedpattern that corresponds to the location of the ends of the traces 416.When the connector end 406 is clamped between the first and secondsurfaces 404 and 410, each electrical contact 409 on the printed circuitboard 411 is in electrical connection with a corresponding trace 416.

Although the exemplary embodiment has electrical contacts located on thehead member 408, the present invention encompasses alternativeembodiments where the electrical contacts 409 are located on the basemember 402 or located on both the head and base members 402 and 408.

In the exemplary embodiment of the connector the first surface 404 ofthe base member 402 includes a layer of foam 418. When the connectionend 406 is locked between the head and base members 402 and 408, thefoam 418 is operative to direct the clamping force of the connectorevenly across the back of the connection end to achieve good electricalconnections between each of the electrical contacts 409 and the traces416.

To further aid the alignment of the traces 416 with the electricalcontacts 409, the connector includes one or more guide pins 424 as shownin FIG. 48. This guide pins 424 are positioned on the base member 402and are operative to guide the edges of the connection end 406 topositions that will achieve the proper registration between the traces416 and electrical contacts 409.

As shown in FIG. 52 a buffer/amplifier 430 is connected to one of thedescribed exemplary connectors 400 to enable the electrical coupling ofa flexible array connection end 436 to the buffer/amplifier 430.

For the exemplary embodiment, both the buffer/amplifier 430 and theconnector 400 are located in a common housing 432. Each of theelectrical contacts in the connector are in electrical connection withthe buffer/amplifier 430 through a cable 431. The housing includes aslot 434 that enables the connection end 436 of a flexible electrodearray to pass through the housing and slide adjacent the base member 444of the connector 400.

In this described embodiment the shaft member 438 of the connectorincludes a lever 440 that extends outside of the housing. The lever 440is operative to rotate the shaft member 438 backward and forward, whichin turn moves the head member between the open and closed positions. Asshown in FIG. 53 the housing 430 may include a clip 442 that enables thebuffer/amplifier 430 to easily attach to a belt around the torso or hipsof a patient. This allows the buffer/amplifier 430 to be easilypositioned as close as possible to the origin of the EMG signals beingcollected from the patient.

The system will now be further described with reference to use of thesensor pad 10 and electrode 28. It should be understood that except asotherwise specified other sensor electrodes, electrode arrays, andsupporting structures may be used in a comparable manner to thatdiscussed herein.

Once sensor pad 10 has been located in position on a patient 48 andsecured by support belt 49 and electrical interconnection made withelectronic apparatus 22, the patient can be moved about and put througha series of different positions in order to develop a series of signalgroups indicative of the underlying musculature. Typically, thesepositions are neutral, flexion, extension, left flexion, right flexion,left rotation, right rotation, sit, supine and prone, although variousmodifiers or alternatives may be added to or deleted from thesepositions. In each of the positions a scan of the electrodes 28 is made,each scan requiring only 1-10 seconds, and the signal informationretained for later utilization in electronic apparatus 22.

Electrical signals from electrodes 28 are connected by way of wires 40,buffer amplifier 42, filters 43, 44 and cable 45 to analog to digital(A/D) converter 24 and then to computer 25 for analysis and conversion.The data from sensor pad 10 is collected in pseudo differential fashion,each electrode 28 being sampled relative to reference electrode 61located in the center of pad 10. Subtraction of electrical data yieldsthe wave form between the two electrodes of interest and the wave formis subjected to a root mean square (RMS) analysis over a predeterminedtime interval to yield a discrete number indicative of the signalstrength. In one example of utilization of the signals, the RMS numberis converted to a representative color indicia and that color indicia isdisplayed on the screen of display unit 26 in a location representativeof the particular two electrodes 28 of interest. This data is preferablyscaled or otherwise conformed to correspond to the anatomy of thepatient as previously discussed using suitable scaling software in thecomputer.

This technique of measurement may best be seen in the FIG. 7representation of a portion of the screen 62 of display unit 26. Herethe electrode positions are represented by circles with alphanumericdesignations therein, with the seven columns of electrodes 28 designatedfrom A-G and the nine rows designated from 1-9. Thus, various electrodepositions are shown, for example, as C4, D5, E6 with D5 representativeof the reference electrode 61 position. Intermediate computer generatedlight bars or line segments 63 interconnect various ones of the adjacentelectrode positions, i.e., C5-D5 and C6-D5 to represent the pattern ofimage generated by computer 25 and displayed at screen 62 of displayunit 26.

A full pattern display is shown in FIG. 3 wherein the screen 62 ofdisplay unit 26 shows the full array of light bars 63 interconnectingall of the electrode 28 positions, in a matrix overlying a display ofthe lower back skeletal anatomy 90 of the patient 48. This viewdemonstrates the spatial relationship among the locations of electrodes28, the visual display of light bars 63 and the patient 48 anatomy 90 ina manner that can be readily visualized and utilized by the examiningphysician. It will be described in greater detail hereinafter that thelight bar 63 display can be adjusted or modified by the physician, orautomatically by the computer to produce effects including a morelimited visual display of light bars 63, or variations in intensity, hueor colorization thereof to enhance the desired display. Further, it willbe shown that instead of the skeletal structure 90 of the patient 48,various depictions of the standard musculature of the patient such asthose templates shown in FIGS. 15-23 can be made to induce a correlationbetween the signals being obtained from the sensing electrodes and thespecific musculature creating the abnormal condition affecting thepatient.

In a scan of the complete array of electrodes 28, 206 color bar imagesare produced on display unit 26 in positions delimited by andcorresponding to the positions of the electrodes 28 on sensor pad 10.Also superimposed on display unit 26 is a graphical depiction of themusculature of the lower back of patient 48 with correlation between thetwo being achieved by the registration process previously describedwhere a sensor pad is located relative to the tenth thoracic vertebrae18 and the PSIS identifying crests 12, 14 or the L4 vertebrae, and usingappropriate scaling.

In a exemplary embodiment of the invention the diagrams of themusculature of FIGS. 15-23, may be shown at the screen of display unit26 as a series of images, each representative of certain muscle groupsof the lower back of patient 48 so that the attending physician mightmake a correlation between the colors which represent the strength ofcontraction of the muscle underneath the electrode and the particularmuscles or muscle groups, and discern what muscle is causing theparticular colorization patterns being produced. It is apparent as well,that it would be possible to program computer 25 to recognize abnormalsignals from the electrodes 28 being polled to provide some otherindication of the abnormal situation using different evaluationtechniques. It is also apparent that the signals collected fromelectrodes 28 can be stored in a database and processed in differentways, perhaps at later times or printed out in hard copy, if this is adesired result. The capture of data from all of the electrodes 28 occurssubstantially simultaneously and is stored in computer 25 formanipulation in a myriad of possible ways, only certain of which aredescribed herein.

Referring now to FIGS. 10-13, there are shown several variations of thetechniques for monitoring and analysis of the electrical signals derivedfrom electrode 28. As previously described, each electrode 28 is scannedrelative to reference electrode 61 to develop a signal representative ofthe voltage level detected at the site of the particular electrode, anddata representative of the signal retained in computer 25. In furtherprocessing of the signals, each signal may be compared to that of otherelectrodes to develop signal patterns representative of the musclecondition being evaluated. For example, FIG. 10 is a representation ofsignals developed at sensor pad 10 when only a depiction of a discretecolor dot is made at the location of each electrode 28, with no showingof color bars. This display might be most useful in achieving a desiredregistration between electrode 28 display and the skeletal structure 90display.

FIG. 11 describes a first variation for analysis of the signals wherethe signal of each electrode 28 in the first row 64 is compared to thecorresponding electrode 28 in the same column, in the second row 65 todevelop a resultant signal, represented at display unit 26 as a bar 66joining the location of the particular electrodes. In this manner a fullpattern of vertical bars 66 is developed, although only a portion isshown, with each being a unique color and representative of the signalcomparison at each electrode pair. Such arrangement of color bars 66 maybe displayed juxtaposed to patterns of muscle structure as previouslydescribed, and likely is more useful in displaying an association withmuscles or muscle groups which are oriented generally vertically in theback of the patient.

FIGS. 12 and 13 represent yet other variations of signal analysiswherein different herringbone patterns of signal are derived. In FIG.12, for example, the signal of center electrode 70 in the second row,center column (D2) is compared with electrodes 71, 72 in the first rowand adjacent columns (C1) (E1) to develop intermediate color bars 74, 75respectively, indicative of the comparison of the electrode signals.Further color bars corresponding to bars 74, 75 are developed throughoutthe array of electrodes 28 to achieve an overall pattern for display atdisplay unit 26. Again, only a portion of the display is depicted inFIG. 12, for purposes of clarity.

FIG. 13 is yet another variation of a display that may be produced usingthis technique of monitoring. Here an inverted herringbone patternconsisting of color bars 78 is achieved when the signals from electrodes28 are compared in the described pattern. For example, electrode 79 inthe first row, center column (D1) is compared to electrodes 80, 81 inthe second row in adjacent columns (C2) (E2) to produce the intermediatecolor bars 78. When extended throughout the array of sensor pad 10, acolored herringbone pattern of color bars 78 is achieved for comparisonwith muscle pattern displays shown in association therewith.

It is apparent that still further comparisons can be made of the signalsobtained from electrodes 28, for example to compare the signal of eachelectrode 28 with the signals of all adjacent electrodes 28, andelectronically summarize the information obtained and to produce arepresentative color pattern of the results for visualization at theface of display unit 26.

Similarly, it is apparent that the resultant electrical signals fromelectrodes 28 and the resultant color information can be shown atdisplay unit 26 in different formats to emphasize the relationshipbetween developed signals and the underlying muscle structure. With asuitably high speed computer 25, the images of differing musclestructures can be shown in association with the color patterns asdirected by the physician to provide a correlation between thecolorization and the abnormal muscle elements.

It will further be understood that in various embodiments differentforms of the display may be used including arrangements of various typesof pixels or other types of icons or designators which are indicative oflevels of muscle activity. While coloration may be a exemplary indicatorin the diagnostic tool for purposes of correlating muscle activity andunderlying anatomy, other visual outputs may be provided which do notinvolve coloration for clinicians who suffer from color blindness. Suchoutputs may involve varying patterns of a monochrome nature which areindicative of levels of muscle activity. Alternatively embodiments ofthe invention may include other types of output devices which enable thediscrimination of levels of muscle activities. Such output devices mayalso output indicia representative of the underlying muscle topography.This may include for example output devices usable by the visuallyimpaired such as pin array type output devices in which arrays of pinsare movable relative to one another to produce surface contours. Sucharrays may be produced with sufficient numbers of pins and pin densitiesto provide contours indicative of underlying musculature as well aselectrical activity. Such devices may be multiplexed between receivedsignals and data representative of underlying musculature to facilitatecomparison through touch of muscle contour and areas of muscle activity.Such output devices may be combined with visual and other type devicesto facilitate diagnosis of conditions even by clinicians who do not havea visual impairment.

Referring now to FIGS. 24 and 25, there is shown in more detail thecomponents comprising the analog and digital signal portions of oneexemplary embodiment of the invention including electrode subsystem 100,analog signal conditioning subsystem 101, and signal processingsubsystem 102. Electrode subsystem 100 comprises the array ofsixty-three electrodes 28, only a few of which are shown and labeled asA, B, F, G, Ref. and Gnd. in correspondence with previous descriptions.Wires 40 connect electrodes 28 to buffer amplifier 42, shown in blockform on FIG. 24 and in more detail in FIG. 25.

A long shielded interconnect cable 104 connects the outputs of bufferamplifier 42 to more remotely located Filter/Buffer module 105 whichincludes low and high pass filters 43, 44. In turn, a short shield cable45 completes the analog signal portion, being connected to analog todigital converter card 24 in computer 25, the latter components beingessential parts of the signal processing subsystem 102. As indicated, asingle continuous shield path, depicted by dashed lines 107, isestablished between Buffer/Amplifier module 42 and computer 25, assuringthat minimal interference is generated in the signals of interest fromextraneous sources.

The enclosures used for the Filter/Buffer module 105 and theBuffer/Amplifier module 42 are shielded with a layer of conductivematerial. All enclosure shields are connected in series with theinterconnect cable shields, resulting in a single continuous shield pathfrom the Buffer/Amplifier input connector to the data acquisitioncomputer 25 chassis ground.

The array of electrodes 28 mounted on sensor pad 10, as previouslydescribed, must conform to the human back, ensure consistent electrodeimpedance with the skin, not interfere substantially with patientmovement, and be easy to use. The electrodes 28 in this describedexemplary embodiment are in a nine row by seven column configuration andthe sensor pad 10 is held in place with a fabric brace with or withoutpressure sensitive adhesive. Of course other configurations ofelectrodes may be used in other embodiments. Likewise the disposabletype and reusable adhesive type sensor arrays discussed previously maybe used.

The analog signal conditioning subsystem 101 provides buffering, voltageamplification and analog filtering for the array of electrodes 28. Inone embodiment one electrode in the array is designated as the referenceelectrode 61, and all other electrode voltages are measured with respectto the reference electrode 61. Other embodiments may employ otherapproaches for acquiring signals indicative of relative levels ofelectrical activity.

Each of the electrode 28 signals is connected by way of wires 40 to highimpedance, unity gain buffer amplifiers 108 by way of a 10K Ohm seriesresistor 109. The purpose of resistor 109 is to provide a measure ofresistive isolation for safety purposes, as well as to increase theelectrostatic discharge (ESD) immunity of the amplifier.

Following the buffer amplifiers 108, each channel has a dedicated highgain instrumentation amplifier 110. The inverting input of eachinstrumentation amplifier 110 is connected to the buffered signal fromthe reference electrode channel as shown by connector 111. Thus, theoutput of each instrumentation amplifier 110 represents the voltage of agiven electrode with respect to the reference electrode 61. RC networks112 connected to the inputs of the instrumentation amplifier 110 serveas low pass filters to block unwanted high frequency signals. Theoutputs of the instrumentation amplifiers 110 feed into unity-gain,line-driver circuits 114 that are capable of driving the capacitive loadof the long shielded interconnect cable 104, without oscillation.

The ground electrode 31 is connected to the patient and is connected toground through a resistor. In one exemplary embodiment electrode 31 isconnected to the analog signal ground on the digital converter cardthrough a one million Ohm resistance. The exemplary form of the analogto digital converter card 24, is a sixty-four channel multiplexedconverter capable of operating in pseudo-differential input mode. TheBuffer/Amplifier module 42 and Filter/Buffer module 105 are eachconnected to ground as represented by line 106.

Each of the sixty-three signal inputs into Filter/Buffer 105, via cable104, is connected to a second order active low pass filter 43. Theoutput of low pass filter 43 is connected to the input of first order,high pass filter 44. The output of each high pass filter 44 is connectedto unity gain buffer 115 that is capable of driving the capacitive loadof the analog to digital converter card 24 interconnect cable 45,without oscillation. Electronic power for Filter/Buffer module 105 isprovided by an external linear power supply. Filter/Buffer module 105provides power for Buffer/Amplifier module 42 via the interconnect cable104. Ground sense line 106 from the Buffer/Amplifier modules 42 passesdirectly through the Filter/Buffer module 105.

Signal processing subsystem 102 is shown in block diagram form in FIG.26 and consists of the major elements of a digital filter 120, voltagedifferencer 121 and RMS calculator 122. First, digital filteringtechniques are used to reduce noise on the measured signal. Next, avoltage differencer 121 determines the voltage waveform between alladjacent electrodes 28. Finally, the root-mean-square (RMS) voltagebetween all adjacent electrodes is calculated and used to characterizethe level of muscle activity between adjacent electrodes. The signalprocessing subsystem is preferably implemented in software on aPC-compatible computer 25.

The digital signal conditioning system consists of high pass, low passand band-cut digital filters incorporated into the data analysissoftware. The high and low pass filters are designed to reject signalsoutside of the frequency range of interest, and have amplitude rolloffsof 80 dB/decade. The primary purpose of these digital filters is toblock common-mode error signals introduced near the corner frequenciesof the analog filters. The band-cut or notch filter drastically reduces60 Hz signals, in order to eliminate unwanted pickup of power lineemissions. In one exemplary form of the invention oversampling is usedwhich interpolates additional pseudo sample points between actual samplepoints to improve performance of filters, for example to achieve goodfrequency discrimination in the 60 Hz notch filter. In one exemplaryembodiment 10× oversampling is used.

The output of the electrode voltage data acquisition subsystem consistsof a set of voltage waveforms of each electrode 28 with respect to aparticular reference electrode. The voltage differencer 121 computes thevoltage waveform between each pair of adjacent electrodes (vertically,horizontally and diagonally) by differencing the voltage waveforms forthe two adjacent electrodes. RMS calculator 122 provides the RMS valueof each adjacent electrode pair waveform as a scalar number which iscomputed from the waveform using a conventional RMS calculation.

The user display subsystem 26 presents the processed data to thepractitioner in a readily understandable format. In the describedembodiment the data is displayed as images on a screen or other visualoutput device. Of course as discussed previously, in other embodimentsother output devices may be used. A digitized illustration of a musclelayer in the human back as shown in FIGS. 14-23 is used as thebackground of the image. The user may select any muscle layer as theimage background. A computer generated image 125 of the processedelectrode 28 data is overlaid on the selected background illustration,and is spatially registered to that image.

As previously discussed the spatial registration may be preferablyachieved through scaling based on the dimensions of the patient input tothe computer.

The electrode data image 125 in the described embodiment consists ofcolored lines or light bars 63 drawn between the locations of each ofadjacent electrodes 28, which are at each intersection 128 of each ofthe seven vertical columns and nine horizontal rows of light bars 63 asshown in FIG. 3 and as has been previously described. The color of eachline 63 indicates the value of the RMS voltage between the adjacentelectrodes. The user can dynamically specify a maximum RMS value and aminimum RMS value which are used to map voltages to colors. Theresulting display is thus a false-color RMS voltage gradient fielddisplay, and is overlaid on and registered to the underlying musclelayer illustration.

The software architecture of the signal processing system 102 is shownschematically in FIG. 27 as a diagram of the main data flow in thesoftware. Essentially, this is a linear flow of computations, each ofwhich takes a datum or file as input and generates a datum or file asoutput. Three types of data files are generated and stored and oncecreated may be opened and displayed many times at later dates. The datafiles are described as well in FIG. 29 and comprise the Analog toDigital (A2D) file 130, Voltage (DAT) file 132 and Root Mean Square(RMS) file 134.

The format of header 135 for each of the files, 130, 132, 134 isdepicted in FIG. 28 and in one embodiment contains information in anidentical ASCII header format consisting of version information 152,patient information 154, which are the vital statistics on the patientbeing diagnosed, pad information 155 which provides specifics of sensorpad 10, calibration information 156, data acquisition settings 157 anddisplay settings 158. The calibration information is derived after thesensor pad 10 location is determined on the back of the patient, beinginput by the operator to specify where certain parts of the patient'sback are in relation to the electrodes on the pad, as previouslydescribed.

The A2D files 130 contain the actual analog to digital values at theoutput of analog to digital converter 24 which are collected during atest. Computer 25 scans all electrode channels rapidly enough toreconstruct the analog signal at all frequencies of interest. In oneembodiment the minimum frequency of interest is about 30 Hz and themaximum about 150 Hz. The structure of the A2D files 130 is shown inFIG. 29 with each scan sample being stored in a two byte word in littleendian format. The files 130 contain the analog to digital value and aheader 135.

The voltage files 132 contain the voltage data from a test, after it hasbeen converted from analog to digital values to voltages and signalconditioning filters have been applied. The voltage files 132 of thisembodiment also contain the header 135 followed by the voltage values inthe format shown in FIG. 29, each sample being stored as an IEEE doublefloating point value.

The RMS files 134 contain the RMS values of the differences between thevoltage waveforms of adjacent electrodes 28. During display of an RMSfile 134, the values can be mapped to colors and displayed as coloredline segments or color bars 63 at display unit 26. Again, the RMS files134 contain header 135 followed by the RMS information. The RMS voltagedifference is calculated for each pair of adjacent electrodes 28. Therow and column position of each of the two electrodes are also stored inthe format described in FIG. 29. Also included is information of theminimum and maximum RMS value in each scan and the total number ofadjacent electrode pairs.

Summarizing then, the flow of data as depicted in FIG. 27 occurs ascomputer 25 generates signals to capture samples 140 from dataacquisition board 24 at the input to computer 25 to create raw data orA2D files 130. Computer 25 then acts to convert the signals to voltageat 142 and run signal conditioning filters 144 to create voltage files132. Computer 25 is then programmed to compute the RMS values at 146 andcreate the RMS data file 134. Subsequently, computer 25 operates toscale and compute color values at 148, and then to draw the RMS data at150 and eventually provide the color bar matrix 125 depicted in FIG. 3.

The general architecture for the software operated in computer 25 can beseen from the source file 160 structure depicted in FIG. 30. Thedocument view and visual interface 161 contain main initialization, menuand toolbar commands, message handlers and document/view commands.Dialog popups 162 allow for entering patient information, calibrationinformation and the like and for editing various parameters. Furtherfiles include data acquisition, filtering and calculation 163, readingand writing header information and data 164, utilities 165, and bitmaps,icons and resource files 166. These routines are fairly typical forhandling the information flow in the ways specified previously and arewell understood in the art, not requiring detailed description herein.Further scaling software components for correlating the storedanatomical data to the anatomy of the particular patient is alsopreferably provided.

Although certain embodiments of the present invention have beendisclosed and specifically described herein, these embodiments are forpurposes of illustration and are not meant to limit the presentinvention. Upon review of this specification, certain improvements,modifications, adaptations and variations upon the methods and apparatusdisclosed which do not depart from the spirit of the present inventionwill immediately become apparent. Accordingly, reference should be hadto the appended claims in order to ascertain the true scope of thepresent invention.

For example, the apparatus of the invention might be applied to areas ofhuman anatomy other than the lower back musculature, most obviously tomid-back, upper back or neck areas. Still further, it would be feasibleto apply the teachings of the invention to the extremities of the humanpatient or even to areas of the head. The present invention may also beapplied to the analysis of signals from other types of sensors and thetechniques described herein used in the diagnosis and treatment of otherconditions. While the exemplary form of the invention is used in thediagnosis of conditions in human beings, the techniques and apparatus ofthe invention may also find applicability in diagnostic and treatmentactivities related to patients which comprise other living organisms.

In addition the teachings of the present invention may also be used fordetecting the position and intensity of other electrical signals withinareas of the anatomy of a living body. Various organs and systems areknown to produce such electrical signals. The analysis of such signalsand their correlation may provide useful information for diagnosis andtreatment.

In addition systems of the present invention may be modified to providetherapeutic benefit as well as to serve a diagnostic function. Forexample electrode arrays may be used to provide electrical stimulusselectively in areas corresponding to the electrodes. Such electricalstimulus may be used to treat muscle or other disorders. By way ofexample an electrode array may be used to determine the identities ofmuscles which are the source of a spasmodic or pain condition in themanner previously discussed. Once such muscles have been identifiedappropriate electrical circuitry may be provided to deliver electricalstimulation selectively so as to treat the underlying muscularstructures. Alternative approaches and techniques may be used based onthe nature of the underlying conditions being detected and theappropriate method of treatment.

Thus the method and apparatus of the present invention achieve the abovestated objectives, eliminates difficulties encountered in the use ofprior devices and systems, solves problems and attains the desirableresults described herein.

In the foregoing description certain terms have been used for brevity,clarity and understanding. However no unnecessary limitations are to beimplied therefrom because such terms are for descriptive purposes andare intended to be broadly construed. Moreover the descriptions andillustrations herein are by way of examples and the invention is notlimited to the details shown and described.

In the following claims any feature that is described as a means forperforming a function shall be construed as encompassing any meanscapable of performing the recited function and shall not be limited tothe particular means shown in the foregoing description or mereequivalents.

Having described the features, discoveries and principles of theinvention, the manner in which it is constructed and operated and theadvantages and useful results attained; the new and useful structures,devices, elements, arrangements, parts, combinations, systems,equipment, operations and relationships are set forth in the appendedclaims.

1. An EMG electrode array comprising: a flexible substrate sheetcomprised of a generally electrically nonconductive material; aplurality of electrically conductive electrodes in operatively supportedconnection with the substrate sheet; a plurality of electricallyconductive trace lines in operatively supported connection with thesubstrate sheet, wherein each electrode includes a respective trace lineextending therefrom, wherein the trace lines are relatively narrowerthan the electrodes, wherein each electrode includes an outsideperimeter, wherein each trace line includes opposed sides; wherein eachportion of the substrate sheet supporting one of the electrodes andsupporting a portion of one of the trace lines that extends from therespective electrode, is bounded in part by at least one perforationthrough the substrate sheet that extends in surrounding relation aroundthe outside perimeter of the one electrode and along the opposed sidesof the portion of the trace line that extends from the respectiveelectrode, such that each of the perforation bounded portions of thesubstrate sheet supporting portions of a respective trace linecorresponds to a bendable stem that is narrower than the perforationbounded portions of the substrate sheet supporting the respectiveelectrode from which the respective trace line extends; wherein thestems of the substrate sheet for each electrode are sufficientlybendable to enable each of the electrodes to move in a plurality ofdirections relative to each other electrode, while maintaining theelectrodes in electrical connection with the trace lines.
 2. The EMGelectrode array according to claim 1, wherein the substrate sheetincludes at least one connection end, wherein each trace line extendsbetween a respective electrode and the at least one connection end ofthe substrate sheet.
 3. The EMG electrode array according to claim 1,wherein the substrate sheet is comprised of a polyester film.
 4. The EMGelectrode array according to claim 1, wherein the electrodes and tracelines are comprised of a conductive ink.
 5. The EMG electrode arrayaccording to claim 4, wherein the electrodes are comprised of an epoxyink including silver.
 6. The EMG electrode array according to claim 1,further comprising an electrically conductive adhesive located on eachelectrode.
 7. The EMG electrode array according to claim 6, wherein theadhesive includes hydrogel.
 8. The EMG electrode array according toclaim 1, further comprising an electrically nonconductive ink depositedover the trace lines.
 9. The EMG electrode array according to claim 1,wherein a portion of each electrode is deposited on the substrate sheetover portions of the trace line that extends therefrom.